Shield structure for electron beam sterilization equipment

ABSTRACT

A shield structure for electron beam sterilization equipment. The shield structure satisfies at least one of the following conditions: (I) an outer diameter D4 of an internal circumferential shield S 4  is larger than an outer diameter D5 of an internal circumferential shield S 5 , and (II) an internal circumferential shield ST 2  of a circular path LT 2  downstream of an entrance trap zone Z 1  connected to an outer-surface sterilization zone Z 2  has an outer diameter DT2 that is larger than an outer diameter D1 of an internal circumferential shield S 1  of a circular path L 1  upstream of the outer-surface sterilization zone Z 2.

TECHNICAL FIELD

The present invention relates to a shield structure for electron beamsterilization equipment that sterilizes containers and instruments forfoods, chemical solutions, and so on by electron radiation.

BACKGROUND ART

When electron beams (cathode rays) emitted for sterilizing cellularmicroorganisms collide with metallic shields (containing lead) disposedas shields, the electron beams are attenuated and then are reflected anddiffracted as X-rays in a widely diffused state. For example, ifelectron beams collide with the shield three or four times, althoughdepending on the intensity thereof, X-rays can be attenuated to a degreeof intensity that does not affect a human body.

For example, if an electron beam irradiation nozzle is inserted into theinlet of a container to sterilize the inner surface of the container,electron beams are emitted from the entire periphery of the electronbeam irradiation nozzle. If a revolving transport device that is arotary device stored in a shield chamber is used to continuouslysterilize the container at a high speed, the container is sterilizedwith the electron beam irradiation nozzle inserted into the inlet, theelectron beam irradiation nozzle being revolved with the container. Inthis case, an electron beam generator cannot turn on or off electronradiation because a high voltage is supplied, leading to continuousradiation. Thus, electron beams (X-rays) leaking from the entrance orexit of the container formed on the shield chamber may be seriouslyshielded or attenuated.

For example, patent literature 1 is proposed as a technique ofsterilizing the inner surface of a container with an electron beamirradiation nozzle inserted into the inlet of the container. Patentliterature 2 proposes the layout of an electron beam irradiation nozzlefor sterilizing an inner surface and an electron beam irradiator forsterilizing an outer surface.

CITATION LIST Patent Literatures Patent Literature 1: NationalPublication of International Patent Application No. 2009-526971 PatentLiterature 2: Japanese Patent Laid-Open No. 2009-35330 (FIGS. 9, 10, 13,15, 16) SUMMARY OF INVENTION Technical Problem

In Patent Literature 1, however, the configuration of the electron beamirradiation nozzle is proposed but a shield is not described.

In Patent Literature 2, the electron beam irradiator is disposed withthe electron beam irradiation nozzle but a shield is not specificallydescribed.

An object of the present invention is to solve the problem and provide ashield structure for electron beam sterilization equipment that canreliably attenuate the leakage of X-rays so as not to adversely affect ahuman body.

Solution to Problem

The first aspect of the present invention is a shield structure forelectron beam sterilization, the shield structure including:

a plurality of shield chambers (R1-R3) each containing each one of aplurality of circular paths (L1-L3) connected in series; whereincontainers are transported along with the circular paths; and asterilization zone (Z2, Z3) including an outer-surface sterilizationzone (Z2) in which the outer surface of a container (B) is sterilized byemitting electron beams to the container (B) from electron beamirradiators (E1, E2) disposed outside first and second circular paths(L1, L2) upstream in a container transporting direction, and aninner-surface sterilization zone (Z3) in which an electron beamirradiation nozzle (En) is inserted into the container (B) transportedalong a third circular path (L3) downstream, and thereby electron beamsare emitted to sterilize an inner surface of the container (B), wherein

the sterilization zone (Z2, Z3) has a container entrance (P0-1) where anentrance trap zone (Z1) for attenuating electron beams is connected anda container exit (P3-4) where an exit trap zone (Z4) for attenuatingelectron beams is connected,

at least one of the entrance trap zone (Z1) and the exit trap zone (Z4)includes more than two of the plurality of circular paths connected inseries, and two or more of the plurality of shield chambers containingthe respective two or more of the plurality of circular paths,

a sterilization zone internal circumferential shield (S1, S2, S3)composed of a metallic shield is mounted along the internalcircumference of each of the circular paths (L1-L3) in the sterilizationzone (Z2, Z3),

a trap zone internal circumferential shield (S4, S5) (ST1, ST2) composedof a metallic shield is mounted on two or more of the plurality of thecircular paths (L4) (LT2) in the entrance trap zone (Z1) and/or the exittrap zone (Z4) (LT2), along the internal circumference of the circularpaths (L4, L5) (LT1, LT2), and

the shield structure satisfies at least one of the conditions (I) and(II):

(I) the circular paths in the exit trap connected to the inner-surfacesterilization zone include a first upstream circular path and a firstdownstream circular path connected to the first upstream circular path,and the internal circumferential shield (S5) of the first downstreamcircular path (L5) has an outer diameter (D5) larger than an outerdiameter (D4) of the internal circumferential shield (S4) of the firstdownstream circular path (L4),(II) the circular paths in the entrance trap zone connected to theouter-surface sterilization zone include a second upstream circular pathand a second downstream circular path connected to the second upstreamcircular path, and the internal circumferential shield (ST2) of thesecond downstream circular path (LT2) has a larger outer diameter (DT2)than an outer diameter (D1) of the internal circumferential shield (S1)of the second upstream circular path (L1).

The second aspect of the present invention is the configurationaccording to the first aspect, wherein the internal circumferentialshield (S5) of the first downstream circular path (L5) has an outerdiameter (D5) 1.3 to 2.5 times larger than the outer diameter (D4) ofthe internal circumferential shield (S4) of the first upstream circularpath (L4) in the exit trap zone (Z4).

The third aspect of the present invention is the configuration accordingto the first aspect, wherein the internal circumferential shield (ST2)of the second downstream circular path (LT2) has an outer diameter (DT2)1.3 to 2.5 times larger than the outer diameter (D1) of the internalcircumferential shield (S1) of the second upstream circular path (L1) inthe entrance trap zone.

The fourth aspect of the present invention is the configurationaccording to the first aspect, wherein in the exit trap zone (Z4), afirst shield chamber (R4) containing a most upstream circular path (L4)has a first attenuating chamber (R4 b) opened to the container exit(P3-4) of the inner-surface sterilization zone, the first attenuatingchamber (R4 b) being formed by dividing the first shield chamber (R4) bya first trap wall (T4) protruding forward to the container exit (P3-4)from a shield wall of the first shield chamber opposed to the containerexit (P3-4).

The fifth aspect of the present invention is the configuration accordingto the first aspect, wherein in the outer-surface sterilization zone(Z2), a second shield chamber (R2) containing a most downstream circularpath (L2) has a second attenuating chamber (R2 b) opened to thecontainer entrance (P2-3) of the inner-surface sterilization zone, thesecond attenuating chamber (R2 b) being formed by dividing the secondshield chamber (R2) by a second trap wall (T2) protruding forward to thecontainer entrance (P2-3) from a shield wall of the second shieldchamber opposed to the container entrance (P2-3).

The reference numerals are identical to those of embodiments.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the first aspect of the present invention, the internalcircumferential shield is mounted along the internal circumference ofthe revolving channel in the sterilization zone. Thus, the number ofreflections of electron beams is increased between the shield chambersand the internal circumferential shields, achieving effectiveattenuation. Moreover, electron beams (X-rays) leaking from thecontainer entrance and the container exit of the shield chamber in thesterilization zone can be effectively blocked by the internalcircumferential shields disposed in a trap zone. This can effectivelyattenuate electron beams (X-rays) leaking upstream and downstream.

In condition (I), a sufficient transport distance and time is necessaryfor the insertion of the electron beam irradiation nozzle and radiation.Thus, the revolving channel needs to be increased in length anddiameter. As the revolving channel of the trap zone disposed at thecontainer exit increases in diameter, the diameter of the revolvingchannel in the inner-surface sterilization zone is limited. Thus, therevolving channel cannot have a large diameter in the trap zone. Thisnecessarily tends to increase an electron beam (X-ray) dose leaking fromthe container exit of the inner-surface sterilization zone to the shieldchamber upstream of the trap zone. In order to address this problem, theouter diameter of the internal circumferential shield of the downstreamrevolving channel is set larger than that of the internalcircumferential shield near the container exit. This can effectivelyblock and reduce a dose of radiation leaking downstream from theupstream shield chamber.

In condition (II), the internal circumferential shield of the revolvingchannel downstream of the entrance trap zone connected to the containerentrance of the outer-surface sterilization zone has a larger outerdiameter than the internal circumferential shield of the revolvingchannel upstream of the outer-surface sterilization zone. This caneffectively block and reduce an electron beam (X-ray) dose leaking fromthe inner-surface sterilization zone and the outer-surface sterilizationzone through the container entrance.

According to the second aspect of the present invention, the outerdiameter of the internal circumferential shield of the downstreamrevolving channel is 1.3 to 2.5 times larger than that of the internalcircumferential shield near the container exit. Thus, the enhancedeffect of blocking and reducing a dose of radiation leaking downstreamfrom the upstream shield chamber can be obtained without excessivelyincreasing the size of a facility.

According to the third aspect of the present invention, the internalcircumferential shield of the revolving channel downstream of theentrance trap zone connected to the container entrance of theouter-surface sterilization zone has an outer diameter 1.3 to 2.5 timeslarger than the outer diameter of the internal circumferential shield ofthe revolving channel upstream of the outer-surface sterilization zone.This can obtain the enhanced effect of blocking and reducing an electronbeam (X-ray) dose leaking from the inner-surface sterilization zone andthe outer-surface sterilization zone through the container entrancewithout excessively increasing the size of a facility.

According to the fourth aspect of the present invention, the trap wallis provided in the shield chamber upstream of the exit trap zone to formthe attenuating chamber. Thus, electron beams (X-rays) leaking from thecontainer exit of the inner-surface sterilization zone can be guidedinto the attenuating chamber by the trap wall. This can effectivelyreflect and attenuate electron beams (X-rays) in the attenuatingchamber.

According to the fifth aspect of the present invention, in theouter-surface sterilization zone, the trap wall is formed in the shieldchamber facing the container entrance, forming the attenuating chamber.Thus, electron beams (X-rays) leaking from the container entrance of theinner-surface sterilization zone can be introduced into the attenuatingchamber by the trap wall and can be effectively reflected and attenuatedin the attenuating chamber.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view schematically showing a first embodiment ofelectron beam sterilization equipment according to the presentinvention.

FIG. 2 is a cross section showing inner-surface and outer-surfacesterilization zones and an exit trap zone in plan view.

FIG. 3 is a longitudinal section showing the electron beam sterilizationequipment, mainly the inner-surface sterilization zone.

FIG. 4A is a longitudinal section of a container lifting/holding device.

FIG. 4B is a cross-sectional view taken along line A-A of FIG. 4A.

FIG. 5 is a plan view showing a driving system for first to sixthrevolving conveyors and a reject revolving conveyor.

FIG. 6 is a longitudinal section showing the first and second revolvingconveyors.

FIG. 7 is a cross-sectional view taken along line B-B of FIG. 6.

FIG. 8 is a longitudinal section showing the fourth to sixth revolvingconveyors.

FIG. 9 is a longitudinal section showing the fifth revolving conveyorand the reject revolving conveyor.

FIG. 10A is a cross section showing a 4-5 connecting opening in planview.

FIG. 10B is a front view showing the 4-5 connecting opening.

FIG. 11A is a plan view showing an irradiation region and a leakageregion of electron beams (X-rays) in the electron beam sterilizationequipment.

FIG. 11B is a plan view showing a reflected leakage region of electronbeams (X-rays) in the electron beam sterilization equipment.

FIG. 12A is a cross section showing an entrance trap zone in plan viewaccording to a first variation.

FIG. 12B is a cross section showing the entrance trap zone in plan viewaccording to a second variation.

FIG. 13A is a longitudinal section showing a container exit chute of areject zone according to a first modification.

FIG. 13B is a longitudinal section showing a container exit chute of thereject zone according to a second modification.

FIG. 13C is a longitudinal section showing a typical container exitchute of the reject zone.

FIG. 14 is a plan view showing a variation of an electron beamirradiator including an electron beam deflector in a second shieldchamber.

FIG. 15 is a cross section showing a second embodiment of electron beamsterilization equipment in plan view according to the present invention.

FIG. 16A is a plan view showing an irradiation region and a leakageregion of electron beams in an entrance trap zone.

FIG. 16B is a plan view showing a reflected X-ray leakage region ofelectron beams in an entrance trap zone.

FIG. 17A is a cross section showing a variation of an internalcircumferential shield in plan view.

FIG. 17B is a cross section showing a variation of an internalcircumferential shield in plan view.

FIG. 17C is a cross section showing a variation of an internalcircumferential shield in plan view.

DESCRIPTION OF EMBODIMENTS First Embodiment

A first embodiment of electron beam sterilization equipment forcontainers including a shield structure according to the presentinvention will be described below with reference to the accompanyingdrawings.

[Outline of Electron Beam Sterilization Equipment]

As shown in FIGS. 1 to 3, electron beam sterilization equipment includesan entrance trap zone Z1, an outer-surface sterilization zone Z2, aninner-surface sterilization zone Z3, and an exit trap zone Z4. Theentrance trap zone Z1 includes a U-shaped feed channel LU. Theouter-surface sterilization zone Z2, the inner-surface sterilizationzone Z3, and the exit trap zone Z4 are configured such that first tosixth revolving channels L1 to L6 for transporting containers B by meansof first to sixth revolving conveyors M1 to M6 are connected in series.Furthermore, on the back of the exit trap zone Z4, a reject zone ZR isprovided to transport insufficiently sterilized ones of the containers Balong a reject revolving channel LR formed by a reject revolvingconveyor MR and eject the transported containers B from a rejectejection port PR.

In the outer-surface sterilization zone Z2, the first and secondrevolving conveyors M1 and M2 forming the first and second circularpaths L1 and L2 are connected in series and are respectively stored infirst and second shield chambers R1 and R2 composed of metallic shields.The first shield chamber R1 contains a first electron beam irradiator E1that sterilizes one outer half surface of the container B by electronbeam irradiation when the container B held by the first revolvingconveyor M1 via a neck n is transported along the first revolvingchannel L1. The second shield chamber R2 contains a second electron beamirradiator E2 that sterilizes the other outer half surface of thecontainer B by electron beam irradiation when the container B held bythe second revolving conveyor M2 via the neck n is transported along thesecond revolving channel L2.

In the inner-surface sterilization zone Z3, a third shield chamber R3composed of a shield contains the third revolving conveyor M3 formingthe third revolving channel L3. The third revolving conveyor M3 includesa plurality of container lifting/holding devices 26 spaced at regularintervals. The container lifting/holding devices 26 hold the containersB via the necks n and sequentially lift the transported containers B toinsert electron beam irradiation nozzles En into the inlets of thecontainers B. Furthermore, third electron beam irradiators E3 that emitelectron beams from the electron beam irradiation nozzles En hung isdisposed on the container lifting/holding devices 26 respectively.

The fourth to sixth revolving conveyors M4 to M6 forming the fourth tosixth circular paths L4 to L6 are connected in series in the exit trapzone Z4. The fourth to sixth revolving conveyors M4 to M6 arerespectively stored in fourth to sixth shield chambers R4 to R6 composedof shields. The fourth to sixth shield chambers R4 to R6 attenuateelectron beams leaking from a 3-4 connecting opening (container exit)P3-4 and X-rays [hereinafter, will be called electron beams (X-rays)]generated by reflecting or diffracting electron beams to the metallicshields. In the fourth to sixth shield chambers R4 to R6, the containersB are held by the fourth to sixth revolving conveyors M4 to M6 via thenecks n and are transported along the fourth to sixth circular paths L4to L6.

The sixth revolving channel L6 is connected to an intermediate revolvingchannel L8 formed by an intermediate revolving conveyor M8. Theintermediate revolving channel L8 is connected to a feeder (not shown)so as to fill the sterilized containers B with a liquid.

The reject zone ZR contains the reject revolving conveyor MR forming thereject revolving channel LR connected to the fifth revolving channel L5.The reject revolving conveyor MR is stored in a reject shield chamber RRsurrounded by a shield.

[The Detail of the Electron Beam Sterilization Equipment ]

The electron beam sterilization equipment is installed in a clean room22 set on a base frame 21 via a structural frame. The first and secondrevolving conveyors M1 and M2 of the outer-surface sterilization zoneZ2, the fourth to sixth revolving conveyors M4 to M6 of the exit trapzone Z4, and the reject revolving conveyor MR of the reject zone ZR areoperated in a synchronized manner with respect to the third revolvingconveyor M3 of the inner-surface sterilization zone Z3.

(Inner-Surface Sterilization Zone)

The third revolving conveyor M3 is set up by a main shaft 23 b that israised on a bottom frame 21D of the base frame 21 so as to penetrate abase top plate 21U. A support table 24 is supported on an outercylindrical shaft 23 a rotatably supported on the main shaft 23 b, and aswiveling table 25 is supported under the outer cylindrical shaft 23 a.The tables are rotated at a predetermined speed along a transportdirection by a revolving transport drive unit 49 shown in FIG. 5. Thesupport table 24 has a plurality of third electron beam generators E3and electron beam irradiation nozzles En connected in a hanging positionto the third electron beam generators E3. The third electron beamgenerators E3 and the electron beam irradiation nozzles En are spaced atregular intervals in a circumferential direction. Reference characterSM3 denotes a third outer shield that shields the third electron beamgenerators E3 on the outer periphery and top surface of the supporttable 24.

The container lifting/holding devices 26 opposed to the electron beamirradiation nozzles En are disposed at equal intervals in thecircumferential direction on the outer periphery of the swiveling table25. The container lifting/holding devices 26 hold the necks n to move upor down the containers B. As shown in FIGS. 4A and 4B, an actuator shaft28 composed of a double cylinder penetrates the swiveling table 25. Theactuator shaft 28 includes a hoisting/lowering outer shaft 28 a that isdisposed on the swiveling table 25 via a thrust bearing 27 so as to moveup and down, and an opening/closing inner shaft 28 b that is fit so asto rotate about an axis in the outer shaft 28 a.

A clamp 31 that can hold the container B via the neck n is provided onthe upper end of the outer shaft 28 a, and a lifting cam mechanism 37that moves up and down the clamp 31 is provided on the lower end of theouter shaft 28 a.

As shown in FIG. 4B, the clamp 31 provided on the upper end of the outershaft 28 a is supported on a base plate 32 fixed on the outer shaft 28 aso as to open and close a pair of clamp arms 35 a and 35 b via a pair ofsupport pins 33. The clamp arm 35 b is operated in synchronization withthe clamp arm 35 a via an interlock pin 34 fixed to the clamp arm 35 avia a plate member, and the clamp arms 35 a and 35 b are urged in aholding direction by a coil spring 30 for closing and urging. Moreover,an opening/closing output cam 36 pivoted by the inner shaft 28 b so asto open and close the clamp arm 35 a is provided between the proximalends of the clamp arms 35 a and 35 b.

The lifting cam mechanism 37 provided on the lower end of the outershaft 28 a has a lifting cam follower 38 that is supported via a liftingarm so as to lift the clamp 31 by rolling the cam surface of the liftingcam 40 mounted on the base frame 21. Reference numeral 41 denotes alifting restraint spring that urges the lifting cam follower 38 to thecam surface of the lifting cam 40.

An opening/closing output cam 36 is attached to the upper end of theinner shaft 28 b and an opening/closing input cam mechanism 42 foropening and closing the clamp 31 is provided on the lower end of theinner shaft 28 b. The opening/closing input cam mechanism 42 has anopening/closing input cam follower 44 that rolls the cam surface of anopening/closing input cam 43 via an opening/closing input arm 45 on theinner shaft 28 b. Reference numeral 46 denotes an opening/closing inputrestraint spring that urges the opening/closing input cam follower 44 tothe cam surface of the opening/closing input cam 43.

The lifting cam 40 is disposed between a 2-3 joint J2-3 and a 3-4 jointJ3-4 of the third revolving channel L3. The opening/closing input cam 43is disposed from the upstream side of the 3-4 joint J3-4 to thedownstream side of the 2-3 joint J2-3.

In this configuration, the container B is transferred via the neck n tothe clamp arms 35 a and 35 b opened by an action of the opening/closinginput cam 43 at the 2-3 joint J2-3 during the rotations of the swivelingtable 25, and then the container B is transported with the neck n heldby the closed clamp arms 35 a and 35 b. After that, the container B islifted via the clamp 31 by an action of the lifting cam 40 so as to fitthe electron beam irradiation nozzle En to the inlet of the container B.Moreover, the inner surface of the container B is sterilized by electronbeams emitted from the electron beam irradiation nozzle En.Subsequently, the container B is moved down via the clamp arms 35 a and35 b by an action of the lifting cam 40 so as to separate the electronbeam irradiation nozzle En from the inlet. When the container Bapproaches the 3-4 joint J3-4, the clamp arms 35 a and 35 b are openedby an action of the opening/closing input cam 43 so as to transfer thecontainer B to the fourth revolving channel L4 with the neck ntransferred to the fourth revolving conveyor M4.

On the inner circumference of the third revolving channel L3, a thirdinternal circumferential shield S3 is disposed between the swivelingtable 25 and the support table 24.

As shown in FIGS. 3, 4A, and 4B, an interlock third ring gear 48 isattached to an outer wall 47 that is hung downward from the outerperiphery of the swiveling table 25 and is rotatably supported on thebase top plate 21U via a ring bearing. As shown in FIG. 5, a conveyordrive gear 50 rotated by a revolving transport drive unit 49 via a speedreducer is engaged with the interlock third ring gear 48.

(Outer-Surface Sterilization Zone)

As shown in FIG. 3, the first and second revolving conveyors M1 and M2are respectively installed in the first and second shield chambers R1and R2 on the base top plate 21U. The first revolving conveyor M1 andthe second revolving conveyor M2 include a first swiveling table 52 anda second swiveling table 72 fixed on the respective upper ends of afirst rotating shaft 51 and a second rotating shaft 71 that rotatablypenetrate the base top plate 21U via bearings. Furthermore, a secondinterlock gear 73 engaged with the interlock third ring gear 48 of thethird revolving conveyor M3 is attached to the lower end of the secondrotating shaft 71, and a first interlock gear 53 engaged with the secondinterlock gear 73 is attached to the lower end of the first rotatingshaft 51. The first interlock gear 53 and the second interlock gear 73are rotated while being interlocked with the outer cylindrical shaft 23a of the third revolving conveyor M3.

The outer peripheries of the first swiveling table 52 and the secondswiveling table 72 have first and second container holders 54 and 74spaced at regular intervals. In this case, the first and secondcontainer holders 54 and 74 are substantially identical in structureexcept for the holding position of the neck n. Thus, only the firstcontainer holder 54 will be discussed below, and the explanation of thesecond container holder 74 denoted by the same reference numerals isomitted. As will be discussed later, fourth to sixth container holders84 and 94 in the exit trap zone Z4 and a reject container holder 114 inthe reject zone ZR are substantially identical in configuration exceptfor the holding position of the neck n, and the detailed explanationthereof is omitted.

As shown in FIGS. 6 and 7, the first container holder 54 includes asupport cylinder 55 vertically penetrating the outer periphery of thefirst swiveling table 52, and a support plate 56 attached to the upperend of the support cylinder 55. A left and right pair of clamp arms 57 aand 57 b is supported on the support plate 56 so as to open and closevia a pair of support pins 58. The clamp arms 57 a and 57 b can beopened and closed with respect to the support pin 58. Specifically, aninterlock pin 60 attached to the one clamp arm 57 a via a plate memberis fit into a receiving groove on the other clamp arm 57 b. The otherclamp arm 57 b can be opened and closed in synchronization with openingand closing of the one clamp arm 57 a via the interlock pin 60. Theinterlock pin 60 is urged in a closing direction by a closing urgingspring 59 connected between ends the clamp arms 57 a and 57 b.

An opening/closing shaft 61 is rotatably supported in the supportcylinder 55, an opening/closing input cam follower 62 is attached to thelower end of the opening/closing shaft 61 via a cam lever, and anopening/closing restraint spring 63 connected to the cam lever bringsthe opening/closing input cam follower 62 into contact withopening/closing input cams 65 attached to the outer cylinder of thefirst rotating shaft 51 so as to coincide with a 0-1 joint J0-1 and a1-2 joint J1-2 that transfer the containers B.

An opening/closing output cam 64 disposed between the proximal ends ofthe clamp arms 57 a and 57 b is attached to the upper end of theopening/closing shaft 61. The rotation of the opening/closing shaft 61can open and close the clamp arm 57 a through the opening/closing outputcam 64.

First and second internal circumferential shields S1 and S2 are mountedon the respective inner peripheries of the first and second circularpaths L1 and L2 on the first and second swiveling tables 52 and 72 ofthe first container holder 54 and the second container holder 74.

A first electron beam irradiator E1 disposed in the first shield chamberR1 and a second electron beam irradiator E2 disposed in a second shieldchamber R2 will be described below.

If the outer surface of the container B is sterilized by electron beamirradiation, the first and second revolving conveyors M1 and M2 providedon the inner circumferences of the first and second circular paths L1and L2 do not allow the installation of an electron beam irradiator.Thus, two electron beam irradiators are disposed on the respective outerperipheries of the two adjacent circular paths to emit electron beams tothe two outer half surfaces of the container B.

In this case, important challenges are: A) to minimize the entry ofcontaminants into the outer-surface sterilization zone Z2 from thecontainer B transported into the first shield chamber R1; B) to minimizethe diffusion of contaminants to one of outer half surfaces of thecontainer B from the other outer half surface before sterilization afterthe one outer half surface is sterilized, and minimize the contaminationof the one sterilized outer half surface; and C) to minimize therecontamination of the container B to the inner-surface sterilizationzone Z3 after the sterilization of the other outer half surface.

Hence, in order to attain A) in the first embodiment, the first electronbeam irradiator E1 for emitting electron beams to the container B islocated near the inlet of the first revolving channel L1, andsterilization on the outer surface of the container B is started with aminimum transport distance and a shortest time, thereby preventing theentry of contaminants from the container B.

In order to attain B), the first electron beam irradiator E1 is mountedon the first revolving channel L1 near the upstream side of the 1-2joint J1-2 of the first revolving channel L1 and the second revolvingchannel L2, and the second electron beam irradiator E2 is mounted nearthe downstream side of the 1-2 joint J1-2 of the second revolvingchannel L2. This minimizes a transport distance and a time period fromthe sterilization of one outer half surface to the sterilization of theother outer half surface.

In order to attain C), the second revolving channel L2 is configured tomaximize the irradiation of electron beams (X-rays) leaking into thecontainer B. The electron beams are emitted from the second electronbeam irradiator E2 in a carry-in channel L2 c from a sterilizationposition on the other outer half surface to the 2-3 joint J2-3, and areemitted from the electron beam irradiation nozzle En of theouter-surface sterilization zone Z2 and leak through a 2-3 connectingopening (container entrance) P2-3.

Specifically, in the first shield chamber R1, the first electron beamirradiator E1 is mounted so as to emit electron beams to the containerB, near the 0-1 joint J0-1 of the U-shaped feed channel LU and the firstrevolving channel L1 of the entrance trap zone Z1 and on the outerperiphery of the first revolving channel L1 near the upstream side ofthe 1-2 joint J1-2. The second electron beam irradiator E2 is mounted onthe outer periphery of the second revolving channel L2 near thedownstream side of the 1-2 joint J1-2 in the second shield chamber R2.The direction of electron beam irradiation is set so as to emit electronbeams from the second electron beam irradiator E2 to the container B onthe second revolving channel L2 opposed to the second electron beamirradiator E2 and the container B on the carry-in channel L2 c on thedownstream side. Since the carry-in channel L2 c faces the P2-3connecting opening of the third shield chamber R3, electron beams(X-rays) leaking from the third shield chamber R3 are also emitted tothe container B.

As shown in FIG. 14, some of electron beams emitted from the secondelectron beam irradiator E2 may be emitted to the container B on acarry-in channel L2 b through at least one electron beam deflector EAafter sterilization.

In the second shield chamber R2, a second chamber trap wall T2 composedof a metallic shield is protruded downstream of the second electron beamirradiator E2 toward the second revolving conveyor M2 from a shield wallR2 a opposed to the 2-3 connecting opening P2-3 of the third shieldchamber R3. The second chamber trap wall T2 forms a second attenuatingchamber R2 b. Thus, electron beams (X-rays) emitted from the 2-3connecting opening P2-3 and the second electron beam irradiator E2 canbe blocked by the second chamber trap wall T2 so as to be guided intothe second attenuating chamber R2 b. This attenuates the electron beamsby reflection.

As shown in FIGS. 6 and 7, the neck n is transferred from the clamp arm57 b of the first container holder 54 to the clamp arm 57 a of thesecond container holder 74 at the 1-2 joint J1-2. The clamp arm 57 b ofthe first container holder 54 holds the neck n at a different positionfrom the clamp arm 57 a of the second container holder 74. Moreover, thefirst electron beam irradiator E1 emits electron beams to one outer halfsurface not held by the clamp arm 57 b on the neck n, and then thesecond electron beam irradiator E2 emits electron beams to the otherouter half surface not held by the clamp arm 57 a on the neck n. Thus,the overall outer surface of the neck n can be sterilized in theouter-surface sterilization zone Z2.

(Entrance Trap Zone)

As shown in FIG. 12A, the entrance trap zone Z1 has a plurality ofconveyor units 11 that form the U-shaped feed channel LU composed of twoconnected quarter arcs

LUi and LUo in plan view, and an entrance trap shield chamber 12 shapedlike a letter U in plan view so as to surround the U-shaped feed channelLU.

The entrance trap shield chamber 12 includes a plurality of first andsecond entrance trap walls T0 a and T0 b that are composed of metallicshields for shielding electron beams (X-rays) leaking from the outersurface and the inner-surface sterilization zones Z2 and Z3, and anentrance attenuating chamber R0 a.

The first entrance trap wall T0 a at the joint of the entrance trapshield chamber 12 and the first shield chamber R1 is protrudedperpendicularly to the shield side wall of the entrance trap shieldchamber 12 (in a crosswise direction) on the opposite side of theU-shaped feed channel LU from the first revolving channel L1. The firstentrance trap wall T0 a can reduce the entry of electron beams (X-rays)from the 0-1 connecting opening (container entrance) P0-1 into theentrance trap shield chamber 12 after the electron beams are emittedfrom the first electron beam irradiator E1, the second electron beamirradiator E2, and the electron beam irradiation nozzles En of the thirdshield chambers R3.

The first entrance attenuating chamber R0 a on the downstream side isopposed to the first shield chamber R1 on the outer periphery of thequarter arc LUo on the downstream side. The first entrance attenuatingchamber R0 a is composed of a surrounding shield wall 12 a thatprotrudes in a rectangular shape from the entrance trap shield chamber12 in plan view. Reference numeral 11 a denotes a not shielded conveyorshield wall provided on the opening of the first entrance attenuatingchamber R0 a so as to surround the conveyor unit 11. The first entranceattenuating chamber R0 a reflects electron beams (X-rays) coming fromthe first shield chamber R1 through the 0-1 connecting opening P0-1,reducing a dose of radiation to the inlet of the entrance trap shieldchamber 12.

The second entrance trap wall T0 b on the upstream side is protrudedfrom the upstream end of the first entrance attenuating chamber R0 a inthe crosswise direction of the U-shaped feed channel LU. Electron beams(X-rays) coming into the first entrance attenuating chamber R0 a areblocked by the second entrance trap wall T0 b, reducing a dose ofradiation from the entrance trap shield chamber 12 to the entrance.

As shown in FIG. 12B, the entrance trap shield chamber 12 may furtherinclude a second entrance attenuating chamber R0 b corresponding to thequarter arc LUi at the inlet, and a third entrance trap wall T0 c. Inthis configuration, the second entrance attenuating chamber R0 b and thethird entrance trap wall T0 c are formed by a surrounding shield wall 12b and are located on the outer periphery of the quarter arc LUi suchthat the second entrance attenuating chamber R0 b and the third entrancetrap wall T0 c are rotated clockwise by 90° in plan view from the firstentrance attenuating chamber R0 a and the second entrance trap wall T0b. This can further considerably reduce a dose of radiation to theentrance of the entrance trap shield chamber 12.

(Exit Trap Zone)

In the exit trap zone Z4, the three fourth to sixth circular paths L4 toL6 formed by the fourth to sixth revolving conveyors M4 to M6 areconnected in series from the 3-4 joint J3-4 on the exit side of thethird revolving channel L3, are connected to a 6-8 joint J6-8 acting asa container ejecting part, and the fourth to sixth revolving conveyorsM4 to M6 are stored in the respective fourth to sixth shield chambers R4to R6 composed of metallic shields.

The fourth to sixth revolving conveyors M4 to M6 are mounted in therespective fourth to sixth shield chambers R4 to R6 on the base topplate 21U. The fourth to sixth revolving conveyors M4 to M6 have fourthto sixth rotating shafts 81, 91, and 101 that rotatably penetrate thebase top plate 21U via bearings, and fourth to sixth swiveling tables82, 92, and 102 that are fixed on the upper end of the fourth to sixthrotating shafts 81, 91, and 101. As shown in FIG. 5, a fourth interlockgear 83 engaged with the interlock third ring gear 48 of the thirdrevolving conveyor M3 is attached to the lower end of the fourthrotating shaft 81, and a fifth interlock gear 93 engaged with the fourthinterlock gear 83 is attached to the lower end of the fifth rotatingshaft 91.

Moreover, a sixth interlock gear 103 engaged with the fifth interlockgear 93 is attached to the lower end of the sixth rotating shaft 101.The fourth to sixth swiveling tables 82, 92, and 102 are rotated whilebeing interlocked with the outer cylindrical shaft 23 a of the thirdrevolving conveyor M3.

The outer peripheries of the fourth to sixth swiveling tables 82, 92,and 102 have fourth to sixth container holders 84, 94, and 104 spaced atregular intervals. Moreover, fourth to sixth internal circumferentialshields S4 to S6 are provided on the respective inner circumferences ofthe fourth to sixth circular paths L4 to L6 on the fourth to sixthswiveling tables 82, 92, and 102.

In this case, the fourth to sixth container holders 84, 94, and 104 aresubstantially identical to the first container holder 54 in structureexcept for the holding position of the neck n. Thus, the containerholders are indicated by the same reference numerals and the explanationthereof is omitted.

The shield structure of the exit trap zone Z4 will be discussed below.

First, the 1-2 to 6-8 connecting openings P1-2 to P6-8 of the 1-2 to 6-8joints J1-2 to J6-8 on the first to sixth circular paths L1 to L6 and areject connecting opening P5-R of a reject joint J5-R on the rejectrevolving channel LR are substantially identical in structure. Thus,referring to FIGS. 10A and 10B, only a 4-5 connecting opening P4-5formed at the 4-5 joint J4-5 will be discussed below and the explanationof the other connecting openings are omitted.

A shield side wall R4W of the fourth shield chamber R4 and a shield sidewall R5W of the fifth shield chamber R5 are overlapped each other with apredetermined clearance. The 4-5 connecting opening P4-5 includes firstand second openings 13 and 14 formed in odd shapes on the two respectiveshield side walls R4W and R5W. In other words, the first opening 13includes a vertically long delivery part 13 a that allows the passage ofthe container B transported on the fifth revolving channel L5 from thefourth revolving channel L4 through the 4-5 joint J4-5, and verticallythe short holder insertion part 13 b that allows the passage of the endsof the clamp arms 57 a and 57 b (35 a, 35 b) moved along the fifthrevolving channel L5. The second opening 14 includes a delivery part 14a that allows the passage of the container B transported on the fifthrevolving channel L5 from the fourth revolving channel L4 through the4-5 joint J4-5, and a holder insertion part 14 b that allows the passageof the ends of the clamp arms 57 a and 57 b (35 a, 35 b) moved along thefourth revolving channel L4. The first and second openings 13 and 14 inodd shapes are formed on the respective shield side walls R4W and R5W,thereby reducing a dose of electron beams (X-rays) leaking from the 4-5connecting opening P4-5.

In the layout of the 4-5 to 6-8 joints J4-5 to J6-8 of the fourth tosixth circular paths L4 to L6, the 4-5 connecting opening P4-5 isdisposed at an angle with respect to the 3-4 connecting opening P3-4;meanwhile, the 4-5 connecting opening P4-5, a 5-6 connecting openingP5-6, and the 6-8 connecting opening P6-8 are substantially linearlydisposed and the fourth to sixth revolving conveyors M4 to M6 aresubstantially linearly disposed. As shown in FIG. 11A, electron beamsdirectly leaking from the 3-4 connecting opening P3-4 of the thirdshield chamber R3 are detected substantially over the fourth shieldchamber R4 but do not reach the back side where the electron beams areblocked by the fourth internal circumferential shield S4 of the fourthrevolving conveyor M4. Electron beams reaching the fifth shield chamberR5 through the 4-5 connecting opening P4-5 are blocked by a fifthinternal circumferential shield S5 of the fifth revolving conveyor M5and do not reach the 5-6 connecting opening P5-6. Thus, it is understoodthat the fifth internal circumferential shield S5 quite effectively actson electron beams reaching the fifth shield chamber R5.

In this case, the outer diameter of the fifth revolving channel L5 isset larger than that of the fourth revolving channel L4, so that anouter diameter D5 of the fifth internal circumferential shield S5 of thefifth revolving conveyor M5 is larger than an outer diameter D4 of thefourth internal circumferential shield S4. This can effectively blockelectron beams (X-rays) leaking from the 3-4 connecting opening P3-4 andthe 4-5 connecting opening P4-5. The outer diameter D5 of the fifthinternal circumferential shield S5 is preferably 1.3 to 2.5 times largerthan the outer diameter D4 of the fourth internal circumferential shieldS4. If the outer diameter D5 is at least 1.3 times larger than the outerdiameter D4, a remarkable shielding effect can be obtained. If the outerdiameter D5 is 1 to 2.5 times larger than the outer diameter D4, afacility does not excessively increase in size. Regarding electron beams(X-rays) that leak from the 3-4 connecting opening P3-4 and collide witha metallic shield, as shown in FIG. 11B, if X-rays generated bycollision with the fourth internal circumferential shield S4 from the3-4 connecting opening

P3-4 leak into the fifth shield chamber R5 through the 4-5 connectingopening P4-5, the X-rays may leak into the sixth shield chamber R6through the 5-6 connecting opening P5-6 as the outer diameter D5 of thefifth internal circumferential shield S5 decreases. Though, an X-raydosage leaking from the 5-6 connecting opening P5-6 into the sixthshield chamber R6 can be substantially eliminated by increasing theouter diameter D5 of the internal circumferential shield S5.

In the fourth shield chamber R4, a fourth chamber trap wall T4 composedof a metallic shield is protruded toward the 3-4 connecting opening P3-4from a shield wall R4 a opposed to the 3-4 connecting opening P3-4 ofthe third shield chamber R3. The fourth chamber trap wall T4 forms afourth attenuating chamber R4 b. Thus, electron beams (X-rays) leakingfrom the electron beam irradiation nozzle En of the third shield chamberR3 to the fourth shield chamber R4 through the 3-4 connecting openingP3-4 can be blocked by the fourth chamber trap wall T4 so as to beguided into the fourth attenuating chamber R4 b. This attenuates theelectron beams by reflection.

The fifth shield chamber R5 contains a fifth chamber trap wall T5substantially vertically protruded from the shield side wall near the5-6 connecting opening P5-6. The fifth chamber trap wall T5 is locatedon the opposite side of the 5-6 connecting opening P5-6 from the rejectchamber RR. The fifth chamber trap wall T5 can reduce a dose ofradiation from the 5-6 connecting opening P5-6 into the sixth shieldchamber R6 by reflecting electron beams (X-rays) on the shield wallafter the electron beams enter from the 4-5 connecting opening P4-5.

[Reject Zone]

For the reject zone ZR for ejecting the insufficiently sterilizedcontainer B when a predetermined electron dose is not obtained, forexample, at a low supplied voltage, the reject revolving conveyor MR ismounted in a clean room 22 and the reject revolving channel LR isformed. In the reject revolving conveyor MR, a reject rotating shaft 111penetrates the base top plate 21U via a bearing, and a reject swivelingtable 112 is attached to the upper end of the reject rotating shaft 111.On the outer periphery of the reject swiveling table 112, rejectcontainer holders 114 identical in structure to the first containerholder 54 are attached at regular intervals. The reject interlock gear113 attached to the lower end of the reject rotating shaft 111 isengaged with the fifth interlock gear 93, allowing the reject swivelingtable 112 to rotate while being interlocked with the outer cylindricalshaft 23 a of the third revolving conveyor M3.

Referring to FIGS. 13A to 13C, exist chutes 121 and 131 mounted on thereject revolving channel LR in the reject zone ZR will be describedbelow.

FIG. 13C shows an exit chute 141 in a typical example. In thisstructure, the container B is fed into a tilted chute body 144 through aceiling tapered part 143 from a container entrance 142 formed so as tocorrespond to the reject ejection port PR, and then the container B isdropped into a tray from a container exit 145. In the case of the exitchute 141, X-rays at the reject ejection port PR with fewer reflectionsare likely to leak directly from the container exit 145.

FIG. 13A shows a first modification of the exit chute 121 formed by ametallic shield wall. In the reject shield chamber RR downstream of thereject ejection port PR, an attenuating chamber 122 having a highceiling is formed with a step, and an entrance ceiling 123 a of thechute body 123 is protruded into the attenuating chamber 122. A bentpart 123 b is formed at an intermediate part of the chute body 123, andthe container exit 123 c is bent downward. In the exit chute 121, X-raysare reflected on the shield wall of the attenuating chamber 122 and thenare reflected on the bent part 123 b and the shield wall of thecontainer exit 123 c. This considerably reduces an X-ray dose leakingfrom the container exit 123 c.

FIG. 13B shows a second modification of the exit chute 131 formed by ametallic shield wall. An attenuating chamber 132, an entrance part 133a, a bent part 133 b, and a container exit 133 c are formed as in thefirst modification. The second modification is different from the firstmodification in that the ceiling part of the attenuating chamber 132 hasa flat surface instead of a step. The exit chute 131 of the secondmodification can obtain the same effect as the first modification.

(Effect of the First Embodiment)

According to the first embodiment, the first and second electron beamirradiators E1 and E2 for sterilizing the outer half surfaces of thecontainer B by electron beam radiation are located close to each othernear the upstream side and the downstream side of the 1-2 joint J1-2 ofthe first and second circular paths L1 and L2 located in theouter-surface sterilization zone Z2. Thus, the other outer half surfacecan be sterilized in a short time after the sterilization of the oneouter half surface. This can considerably reduce recontamination on oneouter half surface by contaminants from the other outer half surface,thereby effectively sterilizing the overall outer surface.

Some electron beams from the second electron beam irradiator E2 areemitted to the container B on the second revolving channel L2 aftersterilization, thereby effectively preventing recontamination on theoverall sterilized outer surface of the container B.

In the outer-surface and inner-surface sterilization zones Z2 and Z3,the first to third internal circumferential shields S1 to S3 are mountedalong the internal circumferences of the first to third circular pathsL1 to L3 in the first to third revolving units M1 to M3. Thus, thenumber of reflections of electron beams is increased between the firstto third shield chambers R1 to R3 and the first to third internalcircumferential shields S1 to S3 of the outer-surface and inner-surfacesterilization zones Z2 and Z3, achieving effective attenuation.

In the exit trap zone Z4, the fourth to sixth internal circumferentialshields S4 to S6 are mounted along the internal circumferences of thefourth to sixth circular paths L4 to L6 in the fourth to sixth revolvingunits M4 to M6. This can effectively block electron beams (X-rays)leaking from the third shield chamber R3 of the inner-surfacesterilization zone Z3 through the 3-4 connecting opening P3-4, therebyeffectively attenuating electron beams (X-rays) leaking downstream.

Furthermore, in the inner-surface sterilization zone Z3, in order toinsert the electron beam irradiation nozzle En into the inlet of thecontainer B and emit electron beams, the container B needs to betransported with a sufficient distance and time. Thus, an extension ofthe third revolving channel L3 requires a larger diameter. As the fourthrevolving channel L4 of the exit trap zone Z4 disposed at the 3-4connecting opening P3-4 increases in diameter, the transport distance ofthe third revolving channel L3 is limited. Thus, the fourth revolvingchannel L4 cannot have a large diameter in the exit trap zone Z4. Thisnecessarily tends to increase an electron beam (X-ray) dose leaking fromthe 3-4 connecting opening P3-4 to the fourth shield chamber R4 upstreamof the exit trap zone Z4.

To address this problem, the outer diameter D5 of the fifth revolvingchannel L5 is set larger than the outer diameter D4 of the fourthinternal circumferential shield S4. Preferably, the outer diameter D5 ofthe fifth internal circumferential shield S5 is 1.3 to 2.5 times largerthan the outer diameter D4 of the fourth internal circumferential shieldS4. This can effectively reduce an electron beam (X-ray) dose leakingdownstream from the fourth shield chamber R4 through the fifth shieldchamber R5.

In the fourth shield chamber R4 of the exit trap zone Z4, the fourthchamber trap wall T4 is provided to form the fourth attenuating chamberR4 b. Thus, electron beams (X-rays) leaking from the 3-4 connectingopening P3-4 of the inner-surface sterilization zone Z3 can beintroduced into the fourth attenuating chamber R4 b and thus can beeffectively reflected and attenuated in the fourth attenuating chamberR4 b.

In the fifth shield chamber R5, the fifth chamber trap wall T5 isprovided on the shield side wall near the 5-6 connecting opening P5-6.This blocks electron beams (X-rays) coming from the 4-5 connectingopening P4-5, reducing a dose of radiation into the sixth shield chamberR6.

In the second shield chamber R2 of the outer-surface sterilization zoneZ2, the second attenuating chamber R2 b is formed by the second chambertrap wall T2 protruding from the shield wall opposed to the 2-3connecting opening P2-3. Thus, electron beams (X-rays) leaking from the2-3 connecting opening P2-3 are introduced into the second attenuatingchamber R2 b by the second chamber trap wall T2, and thus the electronbeams can be effectively reflected and attenuated.

Second Embodiment

Referring to FIGS. 15, 16A and 16B, a second embodiment of electron beamsterilization equipment according to the present invention will bedescribed below. In the second embodiment, an entrance trap zone Z1includes a plurality of circular paths LT1 and LT2.

In the entrance trap zone Z1, the first trap revolving channel LT1 andthe second trap revolving channel LT2 are connected in series between afirst revolving channel L1 and a carry-in revolving channel LS formed bya carry-in revolving conveyor M0. Moreover, a first trap revolvingconveyor MT1 forming the first trap revolving channel LT1 and a secondtrap revolving conveyor MT2 forming the second trap revolving channelLT2 are respectively stored in a first trap shield chamber RT1 and asecond trap shield chamber RT2 that are formed by metallic shield walls.In the carry-in revolving conveyor M0 and the first and second traprevolving conveyors MT1 and MT2, a carry-in part internalcircumferential shield wall S0 and first and second trap internalcircumferential shield walls ST1 and ST2, which are composed of metallicshield walls, are provided along the internal circumferences of thecircular paths LS, LT1, and LT2. Furthermore, on the shield walls of thefirst trap shield chamber RT1 and the second trap shield chamber RT2, atrap entrance P10-1, a trap intermediate PT1-2, and a trap exitconnecting opening PT2-1 substantially identical in structure to thoseof the first embodiment are respectively formed at a trap entrance jointJT0-1 of the carry-in revolving channel LS and the first trap revolvingchannel LT1, a trap intermediate joint JT1-2 of the first trap revolvingchannel LT1 and the second trap revolving channel LT2, and a trap exitjoint JT2-1 of the second trap revolving channel LT2 and the firstrevolving channel L1.

The carry-in revolving unit M0 and the first and second trap revolvingconveyors MT1 and MT2 are identical in configuration to those of thefirst embodiment. Thus, the carry-in revolving unit M0 and the first andsecond trap revolving conveyors MT1 and MT2 are indicated by the samereference numerals and the explanation thereof is omitted.

As shown in FIGS. 16A and 16B, electron beams emitted from the electronbeam irradiation nozzle En of the third shield chamber R3 and the secondelectron beam irradiator E2 hardly enter the second trap shield chamberRT2 directly or as reflected X-rays. However, electron beams emittedfrom the first electron beam irradiator E1 may leak into the second trapshield chamber RT2 from the trap exit connecting opening PT2-1. Toaddress this problem, the outer diameter of the second trap revolvingchannel LT2 is larger than that of the first revolving channel L1, andan outer diameter DT2 of the second trap internal circumferential shieldST2 is larger than an outer diameter D1 of the first internalcircumferential shield S1. The second trap internal circumferentialshield ST2 facing the trap exit connecting opening PT2-1 is so large asto effectively block electron beams (X-rays) leaking from the trap exitconnecting opening PT2-1. Preferably, the outer diameter DT2 of thesecond trap internal circumferential shield ST2 is 1.3 to 2.5 timeslarger than the outer diameter D1 of the first internal circumferentialshield S1. If the outer diameter DT2 is at least 1.3 times larger thanthe outer diameter D1, a remarkable shielding effect can be obtained. Ifthe outer diameter DT2 is 1 to 2.5 times larger than the outer diameterD1, a facility does not excessively increase in size.

In FIGS. 15, 16A and 16B, one shield wall of the trap entranceconnecting opening P10-1 of the first trap shield chamber RT1 isextended because the shield wall has an opening only for the insertionof a container holder.

(Variations of the Internal Circumferential Shield)

In the first and second embodiments, the first to sixth internalcircumferential shields S1 to S6, the intermediate internalcircumferential shield S8, the reject internal circumferential shieldSR, the carry-in internal circumferential shield S0, and the first andsecond trap internal circumferential shields ST1 and ST2 are shaped likecylinders with closed top surfaces in the first to sixth revolvingconveyors M1 to M6, the intermediate revolving conveyor M8, the rejectrevolving conveyor MR, the carry-in revolving conveyor M0, and the firstand second trap revolving conveyors MT1 and MT2. Like an internalcircumferential shield S11 in FIG. 17A, grooves a formed in the axialdirection may be circumferentially spaced at regular intervals on theouter periphery shaped cylindrically. Like an internal circumferentialshield S12 in FIG. 17B, reflecting plates b protruded along the axialdirection may be circumferentially spaced at regular intervals on theouter periphery of the cylinder. Like the internal circumferentialshield S13 in FIG. 17C, shield plates c crossing one another at the axismay be radially assembled at a predetermined angle.

The internal circumferential shields S11 to S13 can more effectivelydiffuse incident electron beams so as to accelerate attenuation.

1. A shield structure for electron beam sterilization, the shieldstructure comprising: a plurality of shield chambers each containingeach one of a plurality of circular paths connected in series, whereincontainers are transported along with the circular paths; and asterilization zone including an outer-surface sterilization zone inwhich an outer surface of the container is sterilized by emittingelectron beams to the container from electron beam irradiators disposedoutside first and second circular paths upstream in a containertransporting direction, and an inner-surface sterilization zone in whichan electron beam irradiation nozzle is inserted into the containertransported along a third circular path downstream in the containertransporting direction, and thereby electron beams are emitted tosterilize an inner surface of the container, wherein the sterilizationzone has a container entrance where an entrance trap zone forattenuating electron beams is connected and a container exit where anexit trap zone for attenuating electron beams is connected, at least oneof the entrance trap zone and the exit trap zone includes more than twoof the plurality of circular paths connected in series, and two or moreof the plurality of shield chambers containing the respective two ormore of the plurality of circular paths, a sterilization zone internalcircumferential shield composed of a metallic shield is mounted along aninternal circumference of each of the circular paths in thesterilization zone, a trap zone internal circumferential shield composedof a metallic shield is mounted on two or more of the plurality of thecircular paths in the entrance trap zone and/or the exit trap zone alongthe internal circumference of the circular path, and the shieldstructure satisfies at least one of conditions (I) and (II): (I) thecircular paths in the exit trap connected to the inner-surfacesterilization zone include a first upstream circular path and a firstdownstream circular path connected to the first upstream circular path,and the internal circumferential shield of the first downstream circularpath has a larger outer diameter than an outer diameter of the internalcircumferential shield of the first upstream circular path, (II) thecircular paths in the entrance trap zone connected to the outer-surfacesterilization zone include a second upstream circular path and a seconddownstream circular path connected to the second upstream circular path,and the internal circumferential shield of the second downstreamcircular path has a larger outer diameter than an outer diameter of theinternal circumferential shield of the second upstream circular path. 2.The shield structure for electron beam sterilization according to claim1, wherein the internal circumferential shield of the first downstreamcircular path has an outer diameter 1.3 to 2.5 times larger than theouter diameter of the internal circumferential shield of the firstupstream circular path in the exit trap zone.
 3. The shield structurefor electron beam sterilization according to claim 1, wherein theinternal circumferential shield of the second downstream circular pathhas an outer diameter 1.3 to 2.5 times larger than the outer diameter ofthe internal circumferential shield of the second upstream circular pathin the entrance trap zone.
 4. The shield structure for electron beamsterilization according to claim 1, wherein in the exit trap zone, afirst shield chamber containing a most upstream circular path has afirst attenuating chamber opened to the container exit of theinner-surface sterilization zone, the first attenuating chamber beingformed by dividing the first shield chamber by a first trap wallprotruding forward to the container exit from a shield wall of the firstshield chamber opposed to the container exit.
 5. The shield structurefor electron beam sterilization according to claim 1, wherein in theouter-surface sterilization zone, a second shield chamber containing amost downstream circular path has a second attenuating chamber opened tothe container entrance of the inner-surface sterilization zone, thesecond attenuating chamber being formed by dividing the second shieldchamber by a second trap wall protruding forward to the containerentrance from a shield wall of the second shield chamber opposed to thecontainer entrance.